System, a device and a method for adjusting output power in a distributed amplifier system

ABSTRACT

A system comprises a first device and a second device. The first device comprises a receiver, a spectrum analyzer, a controller, an amplifier, a filter and a transmitter. The first device receives from at least one antenna a plurality of signals from different sources. The spectrum analyzer is coupled to the receiver and determines whether a downlink signal power from each of the sources to the system exceeds a predetermined threshold. The controller is coupled to the spectrum analyzer and generates a first indication indicating lowering gains of an amplifier on signals from at least one source with downlink signal power larger than the predetermined threshold. The amplifier is coupled to the controller and lowers gains of the amplifier according to the indication from the controller. The transmitter transmits the plurality of signals after adjustment to at least one second device distributed within a site.

CROSS-REFERENCE TO RELATED APPLICATION(S)

The present application claims the benefit of and incorporates by reference U.S. provisional application No. 61/749,922, entitled “Intelligent Distributed Amplifier System,” which was filed on Jan. 8, 2013.

TECHNICAL FIELD

The present disclosure relates to a telecommunication system, and more particularly, but not exclusively to a system, a device and a method for adjusting signal output power in a distributed amplifier system.

BACKGROUND

In a distributed amplifier system (DAS), when the DAS system is located very close to the communications network source signal such as a cellular tower, a power of a communication device can be so low that it may result in degraded performance or a dropped call.

In order to protect the communications network, the DAS will lower the output power to where the noise is below the noise floor of the communications system. Unfortunately, lowering the output power of the DAS amplifier will lower the output power for communication signals that are going to different communication systems from different network providers, therefore reducing the effectiveness of the DAS for the wireless devices using a variety of communication networks. Therefore, a system and method for improving adjusting of signal output power across sub-bands may be needed.

SUMMARY OF THE INVENTION

According to an embodiment of the invention, a system comprises a first device and a second device. The first device comprises a receiver, a spectrum analyzer, a controller, an amplifier, a filter, and a transmitter. The first device receives, from at least one antenna, a plurality of signals from different sources.

The spectrum analyzer is communicatively coupled to the receiver and determines whether a downlink signal power from each of the sources to the system exceeds a predetermined threshold. The controller is communicatively coupled to the spectrum analyzer and generates a first indication indicating lowering gains of an amplifier on signals from at least one source with downlink signal power larger than the predetermined threshold. The amplifier is communicatively coupled to the controller and lowers gains of the amplifier according to the indication from the controller. The transmitter transmits the plurality of signals after adjustment to at least one second device distributed within a site. The at least one second devices transmits the plurality of received signals after adjustment within the site.

In another embodiment, a first device comprises a receiver, a spectrum analyzer, a controller and a transmitter. The receiver receives, from at least one antenna, a plurality of signals from different sources. The spectrum analyzer is communicatively coupled to the receiver and determines whether a downlink signal power from each of the sources to the system exceeds a predetermined threshold. The controller is communicatively coupled to the spectrum analyzer and generates an indication indicating lowering gains on signals from at least one source with a downlink signal power larger than a predetermined threshold. The amplifier is communicatively coupled to the controller and lowers gains of the amplifier according to the indication from the controller. The transmitter transmits the plurality of signals after adjustment to at least one second device distributed within a site.

In another embodiment, a method comprises receiving, from at least one antenna, a plurality of signals from different sources; determining whether a downlink signal power from each of the sources to the system exceeds a predetermined threshold; lowering gains on signals from at least one source with a downlink signal power larger than the predetermined threshold; transmitting the plurality of signals after adjustment to a plurality of second devices distributed within a site.

In another embodiment, a system comprises a plurality of first devices and a second device. The first devices are distributed in a site each comprising a first transmitter configured to transmit at least one signal to a second device. The second device comprises a receiver, a spectrum analyzer, a controller, an amplifier and a transmitter. The receiver receives a plurality of signals from the plurality of first devices. The spectrum analyzer determines whether a downlink signal power from a source to the system exceeds a predetermined threshold. The controller is communicatively coupled to the spectrum analyzer and generates an indication indicating lowering gains on signals from the first device to the second device when a downlink signal power from the source to the system exceeds a predetermined threshold. The amplifier is communicatively coupled to the controller and lowers gains of the amplifier according to the indication from the controller. The transmitter configured to transmit the plurality of signals after adjustment to the source.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention is illustrated in an exemplary manner by the accompanying drawings. The drawings should be understood as exemplary rather than limiting, as the scope of the invention is defined by the claims. In the drawings, like references indicate similar elements.

FIG. 1A is a diagram illustrating a deployment of distributed amplifier system.

FIG. 1B is a block diagram illustrating a detailed embodiment of the distributed amplifier system.

FIG. 2 is a diagram illustrating a block diagram of a different embodiment of the distributed amplifier system.

FIG. 3 is a block diagram illustrating a different embodiment of a first device of FIGS. 1A and 1B.

FIG. 4 is a flow chart illustrating an embodiment of a method.

FIG. 5 is a block diagram illustrating another embodiment of a first device operating in uplink transmission.

DETAILED DESCRIPTION

FIG. 1A is a diagram illustrating a deployment of a distributed amplifier system 10A. The cellular signals from outdoor cellular towers may not provide clear and consistent coverage inside buildings, so wireless operators and building owners use distributed antenna systems 10A to broadcast cellular signals throughout their sites. Note that the cellular signals are for illustration, and it may also include Wi-Fi signals, satellite signals, and other communication signals. The communications signals are distributed throughout building interiors, campus environments, and outdoor areas using an active Distributed Amplifier System (DAS). The DAS is active because it uses signal amplifiers to add gain to communications radio frequency (RF) signals. This gain also facilitates penetration of the signals throughout a building, campus environment, or outdoor areas despite physical obstructions such as walls, interior structures, poles, and trees without loss of signal integrity.

The distributed amplifier system 10A comprises a head end 100, a plurality of coverage nodes 150 and roof mounted antenna(s) 180. The distributed amplifier systems 10A work by distributing wireless signals throughout an interior space: the signal is typically brought to the building using roof-mounted antennas 180 or with a base station (BTS) installed in a telecommunications equipment room. The antennas 180 or BTS is then connected to the DAS using coaxial cabling or other wired or wireless connection mechanism. The DAS network of coverage nodes 150 is placed strategically throughout the building using cable or other connection mechanism. The DAS works with multiple coverage nodes 150 strategically placed within the building to provide reliable text messaging, data, and voice communications. All coverage nodes 150 in the system may be networked together to deliver a balanced and reliable signal throughout the site. The head end unit 100 manages all of the coverage nodes 150 in the DAS system along with local and remote access for monitoring and status checking. Alternatively, management may be distributed across the network.

Alternatively, the DAS system can be installed in any site, which may include tunnels, fields, sports stadiums, subway or railway stations, buses, airports, or subways, etc. in additional to the building shown in FIG. 1A.

FIG. 1B is a block diagram illustrating a detailed embodiment 10B of the distributed amplifier system 10A shown in FIG. 1A. A distributed amplifier system 10B shown in FIG. 1B comprises a head end 100 and a plurality of coverage nodes 150. The head end 100 comprises a sub-band limiting unit 102, a Pilot Tx (Transmit) unit 104, a bi-directional cellular amplifier 106, a modem 108, a spectrum analyzer 110, a calibration info unit 112, a characterization unit 114, and a remote connect unit 116.

The sub-band limiting unit 102 is communicatively coupled to the antenna 180 and limits strength of sub-band signals. The bi-directional cellular amplifier 106 is communicatively coupled to the sub-band limiting unit 102 and amplifies the sub-band signals. The bi-directional cellular amplifier 106 is also communicatively coupled to the pilot Tx unit 104, so that the bi-directional cellular amplifier 106 can obtain information regarding how close the coverage antennas 156 are to each other from the pilot Tx unit 104. The bi-directional cellular amplifier 106 is further communicatively coupled to the modem 108, so that the amplified signals are delivered to the modem 108. The modem 108 is part of an internal network for access and control of the DAS. To be more specific, the modem 108 is a communication device that talks to all of the remote nodes including but not limited to modems 154. The spectrum analyzer 110 is communicatively coupled to the sub-band limiting unit 102 and analyzes spectrum of the signals outputted by the sub-band limiting unit 102. The calibration information unit 112 is communicatively coupled to the spectrum analyzer 110 and collects calibration information from the spectrum analyzer 110. The calibration info unit 112 is the place where all of the calibration information for all nodes and the head end are stored. This calibration information is used by the characterization unit 114 to determine if the environment has changed. The characterization unit 114 is communicatively connected to the calibration information unit 112 and observes the way the unit is calibrated and then monitors the entire DAS system to determine if the environment is change that needs re-calibration. The characterization unit 114 can be used to trigger trouble shooting in the system. The remote connect unit 116 is communicatively connected to the characterization unit 114 and transmits remote connect information through the antenna 190 or via other wired or wireless connection mechanism. The Pilot Tx unit 104 is a Pilot transmitter, and is used to measure how close the coverage antennas are to each other. The term “communicatively couple” includes any kinds of coupling, such as wired or wireless connection.

While only one amplifier 106 is shown in the first device 100, in an embodiment of the invention, there are multiple amplifiers to amplify different frequencies. Further, while the amplifier 106 is referred to as a cellular amplifier, it can also amplify other signals, such as WiFi, WiMax, public emergency signals etc. Similarly, while only one amplifier 152 is shown in the second device 150, in an embodiment of the invention, there are multiple amplifiers to amplify different frequencies. Further, while the amplifier 152 is referred to as a cellular amplifier, it can also amplify other signals, such as WiFi, WiMax, public emergency signals etc. Further, the amplifier may also be a single direction amplifier, such as uplink or downlink.

While only one sub-band limiting unit 102 is shown in the first device 100, in an embodiment of the invention, there are multiple sub-band limiting units 102 to filter signals in different sub-bands.

Each of the coverage node 150 comprises a bi-directional cellular amplifier 152 and a modem 154. The bi-directional cellular amplifier 152 is communicatively coupled to the modem 154. The uplink and downlink signals are amplified by the bi-directional cellular amplifier 152. Each of the cellular amplifier is also communicatively coupled to an antenna 156 to transmit downlink signals to user equipment attached to or covered by the coverage nodes 150, or receive uplink signals from the user equipment attached to or covered by the coverage nodes 150. The head end 100 and each of the coverage nodes 150 are connected by coaxial cable or other wired or wireless connection mechanism.

Each of the various modules shown in FIG. 1B (e.g., Calibration info unit 112) can be implemented in pure hardware (e.g., specially-designed dedicated circuitry such as one or more application-specific integrated circuits (ASICs)), or in programmable circuitry appropriately programmed with software and/or firmware, or in a combination of pure hardware and programmable circuitry.

FIG. 2 is a diagram illustrating a detailed embodiment 10C of the distributed amplifier system 10A shown in FIG. 1A. The distributed amplifier system 10C shows units or modules pertinent to the embodiment. The system 10C comprises a first device 100A and at least one second devices 150. The first device 100A comprises a receiver 200, a spectrum analyzer 110, a controller 210, an amplifier 106 and a transmitter 220. The first device 100A may be implemented by the head end 100 shown in FIGS. 1A and 1B. The second devices 150 shown in FIG. 2 are substantially the same as the second devices 150 shown in FIGS. 1A and 1B. An interconnect 230 shown in FIG. 2 is an abstraction that represents any one or more separate physical buses, point-to-point connections, wired or wireless connections. The interconnect 230, therefore, may include, for example, a system bus, a form of Peripheral Component Interconnect (PCI) bus, a HyperTransport or industry standard architecture (ISA) bus, a small computer system interface (SCSI) bus, a universal serial bus (USB), IIC (I2C) bus, a CAN-bus (Controller Area Network), or an Institute of Electrical and Electronics Engineers (IEEE) standard 1394 bus, also called “Firewire”, and/or any other suitable form of physical or virtual connection, either wired or wireless.

The receiver 200 receives, from at least one antenna, a plurality of signals from different sources. The source includes but is not limited to a telecommunication tower such as a cellular tower, an access point such as a Wi-Fi hot spot, or a satellite signal transmitter, etc. The spectrum analyzer 110 is communicatively coupled to the receiver 200 and determines whether a downlink signal power from each of the sources to the system exceeds a predetermined threshold. The predetermined threshold may be a value between −60 dBm to −40 dBm. The downlink signal power or strength is an indicator of a distance between the source (not shown in FIG. 2) and a DAS system 10C. Examples of source include a cellular tower, a WIFI hotspot. The closer the DAS system 10C to the source, the larger the downlink signal power between the source and the DAS system. By contrast, the farther the DAS system 10C to the source, the smaller the downlink signal power between the source and the DAS system. The controller 210 is communicatively coupled to both the spectrum analyzer 110 and an amplifier 106 and configured to generate a first indication indicating lowering gains of the amplifier 106 on signals from at least one source with downlink signal power larger than the predetermined threshold. The amplifier 106 adjusts gains according to the first indication from the controller 210. In other words, the gains of signals on the sub-band from the source nearer to the DAS system are lowered compared to the other signals on other sub-band across the band. The filters are configured so that each of the different radio frequency (RF) sub-band may be handled independently.

When the distributed amplifier system is closer to the tower, not as much signal gain is required as what is needed for a tower farther away. Since the distributed amplifier system is closer to that tower, it doesn't need a strong signal. The communication quality for a signal with a lower signal strength will not deteriorate when the DAS system is closer to the source.

Further, noise refers to the noise emitted into the cellular network from an amplifier system. Noise is emitted because amplifier system amplifies the wanted cellular signal together with the noise contained in the air at the input antenna. The more gain an amplifier system has, the more noise it emits. The noise may include “white noise”, and is spread out across all frequencies. In order not to have a negative effect on the cellular network, gains are reduced when the signal is from nearer cellular towers. Therefore, lowering the output power on an amplifier for signal from a nearer source will not affect the output power for communication signals that are going to different communication systems from different network providers. The gain on the sub-bands used by the nearby towers are lowered thus lowering the noise on this sub-band, while still providing high gain on the sub-bands used by far away towers. As a result, the effectiveness of the DAS system for the wireless devices using a variety of communication networks can be improved.

In another embodiment, the first indication further comprises lowering output power of the signals from at least one source with downlink signal power larger than the predetermined threshold such that noises of the plurality of signals after adjustment are below a predetermined noise floor. The predetermined noise floor may be −100 dBm.

The transmitter 220 transmits the plurality of signals after adjustment to at least one of the second devices 150 distributed within a site.

Alternatively, the controller 210 may further generate a second indication indicating increasing gains on signals from at least one source with downlink signal power smaller than or equal to the predetermined threshold. In other words, the output power of an amplifier for signal from a farther source will be increased.

FIG. 3 is a block diagram illustrating a different embodiment 1008 of the first device 100A shown in FIG. 2. Details are omitted for elements already described with respect to FIG. 2. Compared to FIG. 2, the first device 1008 further comprises a filter 300. The filter 300 is also communicatively coupled to the controller 210. The filter 300 also adjusts output power of the signals on specific sub-bands indicated by the controller 210. For example, the filter 310 lowers the output power of the signal on the sub-band from a source with a larger downlink signal power.

The filter 300 may include a radio frequency (RF) filter configured to lower output power of the signals from the at least one source with downlink signal power larger than the predetermined threshold. Alternatively, the filter 300 may include a synthesizer configured to lower output power of the signals from the at least one source with downlink signal power larger than the predetermined threshold. Alternatively, the filter 300 may comprise a digital signal processing (DSP) unit configured to lower output power of the signals from the at least one source with downlink signal power larger than the predetermined threshold. The interconnect 230 shown in FIG. 4 is substantially the same as the interconnect 230 shown in FIG. 2, which represents the interconnection among the receiver 200, the spectrum analyzer 114, the filter 400, the controller 410 and the transmitter 220.

In another embodiment, the receiver 200, the controller 210, the filter 300, the amplifier 106 and the spectrum analyzer 110, and the transmitter 220 are connected in serial. The filter 400 may change the signal to make it more flat, and the output of this filter 400 may feed into the transmitter 220 and the spectrum analyzer 110. In other words, the filter 300 will alter what the spectrum analyzer 110, the amplifier 106 and the transmitter 220 will get.

FIG. 4 is a flow chart illustrating an embodiment of a method 40. The method 40 comprises receiving (in block 410), from at least one antenna, a plurality of signals from different sources, determining (in block 420) whether a downlink signal power from each of the sources to the system exceeds a predetermined threshold; lowering (in block 430) gains on signals from at least one source with a downlink signal power larger than the predetermined threshold; transmitting (in block 440) the plurality of signals after adjustment to at least one second devices distributed within a site.

The above embodiment illustrates a downlink transmission scenario. In uplink transmission, however, directions of all the arrows are reversed in respect to the direction shown in FIG. 1B. In other words, the arrows are upstream for the uplink scenario. FIG. 5 is a diagram illustrating another embodiment 100 of the distributed system 10A operating for uplink transmission. The distributed amplifier system 100 comprises a plurality of second devices 150 and a first device 100A. The plurality of second devices 150 are distributed in a site. Each second device 150 comprises a first transmitter 500 that transmits at least one signal to the first device 100A. The first device 100A comprises a receiver 510, a spectrum analyzer 110, a controller 210, an amplifier 106, and a second transmitter 520. The receiver 510 receives a plurality of signals from the plurality of second devices 150. The spectrum analyzer 110 is communicatively coupled to the receiver 510 and determines whether a downlink signal power from a source to the system exceeds a predetermined threshold. The controller 210 is communicatively coupled to the spectrum analyzer 110 and generates an indication indicating lowering gains on output power of signals from the second device 500 to the first device 100A when a downlink signal power from the source to the system exceeds a predetermined threshold. The amplifier then lowers the output power of the received signals according to the indication from the controller 210. The second transmitter 520 transmits the plurality of signals after adjustment to the source. Therefore, lowering the output power of an amplifier for signal to a nearer source will not affect the output power for communication signals that are going to different communication systems from different coverage nodes, therefore the effectiveness of the DAS for the wireless devices using a variety of communication networks can be improved. Note that the downlink signal which is used by the spectrum analyzer 110 are different from the uplink signals received by the receiver 510 from the second device 150, adjusted by the amplifier and then transmitted by the second transmitter 520.

Further, noise refers to the noise emitted into the cellular network from an amplifier system. Noise is emitted because any amplifier system amplifies the wanted cellular signal together with the noise contained in the air at the input antenna. The more gain an amplifier system has, the more noise it emits. In order not to have a negative effect on the cellular network, gains are reduced for uplink signal to nearer the cellular towers. Therefore, lowering the output power on an amplifier for signal to a nearer source will not affect the output power for communication signals that are going to different communication systems from different network providers. The gain on the sub-bands used by the nearby towers are lowered thus lowering the noise on this sub-band, while still providing high gain on the sub-bands used by far away towers. As a result, the effectiveness of the DAS system for the wireless devices using a variety of communication networks can be improved.

Note that any and all of the embodiments described above can be combined with each other, except to the extent that it may be stated otherwise above or to the extent that any such embodiments might be mutually exclusive in function and/or structure.

Although the present invention has been described with reference to specific exemplary embodiments, it will be recognized that the invention is not limited to the embodiments described, but can be practiced with modification and alteration within the spirit and scope of the appended claims. Accordingly, the specification and drawings are to be regarded in an illustrative sense rather than a restrictive sense.

From the foregoing, it will be appreciated that specific embodiments of the invention have been described herein for purposes of illustration, but that various modifications may be made without deviating from the scope of the invention. Accordingly, the invention is not limited except as by the appended claims.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. Even if certain features are recited in different dependent claims, the present invention also relates to an embodiment comprising these features in common. Any reference signs in the claims should not be construed as limiting the scope.

Features and aspects of various embodiments may be integrated into other embodiments, and embodiments illustrated in this document may be implemented without all of the features or aspects illustrated or described. One skilled in the art will appreciate that although specific examples and embodiments of the system and methods have been described for purposes of illustration, various modifications can be made without deviating from the spirit and scope of the present invention. Moreover, features of one embodiment may be incorporated into other embodiments, even where those features are not described together in a single embodiment within the present document. Accordingly, the invention is described by the appended claims. 

I/We claim:
 1. A system comprising: a first device comprising a receiver configured to receive, from at least one antenna, a plurality of signals from different sources; a spectrum analyzer communicatively coupled to the receiver and configured to determine whether a downlink signal power from each of the sources to the system exceeds a predetermined threshold; a controller communicatively coupled to the spectrum analyzer and configured to generate a first indication indicating lowering gains of an amplifier on signals from at least one source with downlink signal power larger than the predetermined threshold; the amplifier communicatively coupled to the controller and configured to lower gains of the amplifier according to the indication from the controller; a transmitter configured to transmit the plurality of signals after adjustment to at least one of the second device distributed within a site; and the at least one second devices configured to transmit the plurality of received signals after adjustment within the site.
 2. The system of claim 1, wherein the controller is also configured generate a second indication indicating increasing gains on signals from at least one source with downlink signal power smaller than or equal to the predetermined threshold.
 3. The system of claim 1, wherein the first indication further comprises lowering output power of the signals from at least one source with downlink signal power larger than the predetermined threshold such that noises of the plurality of signals after adjustment are below a predetermined noise floor.
 4. The system of claim 1, further comprising a filter communicatively coupled to the controller, wherein the filter includes a radio frequency (RF) filter configured to lower output power of the signals from the at least one source with downlink signal power larger than the predetermined threshold.
 5. A system of claim 1, further comprising a filter communicatively coupled to the controller, wherein the filter includes a synthesizer configured to lower output power of the signals from the at least one source with downlink signal power larger than the predetermined threshold.
 6. A system of claim 1, further comprising a filter communicatively coupled to the controller, wherein the filter further comprises a digital signal processing (DSP) unit configured to lower output power of the signals from the at least one source with downlink signal power larger than the predetermined threshold.
 7. The system of claim 1, wherein the first device comprises a head end, and the second device comprises a coverage node.
 8. A first device comprising a receiver configured to receive, from at least one antenna, a plurality of signals from different sources; a spectrum analyzer communicatively coupled to the receiver and configured to determine whether a downlink signal power from each of the sources to the system exceeds a predetermined threshold; a controller communicatively coupled to the spectrum analyzer and configured to generate an indication indicating lowering gains on signals from at least one source with a downlink signal power larger than a predetermined threshold; an amplifier communicatively coupled to the controller and configured to lower gains of the amplifier according to the indication from the controller; and a transmitter configured to transmit the plurality of signals after adjustment to at least one second device distributed within a site.
 9. A method comprising: receiving, from at least one antenna, a plurality of signals from different sources; determining whether a downlink signal power from each of the sources to the system exceeds a predetermined threshold; lowering gains on signals from at least one source with a downlink signal power larger than the predetermined threshold; transmitting the plurality of signals after adjustment to a plurality of second devices distributed within a site.
 10. A system comprising: A plurality of first devices distributed in a site each comprising a first transmitter configured to transmit at least one signal to a second device; and the second device comprising a receiver configured to receive a plurality of signals from the plurality of first devices; a spectrum analyzer configured to determine whether a downlink signal power from a source to the system exceeds a predetermined threshold; and a controller communicatively coupled to the spectrum analyzer and configured to generate an indication indicating lowering gains on signals from the first device to the second device when a downlink signal power from the source to the system exceeds a predetermined threshold; an amplifier communicatively coupled to the controller and configured to lower gains of the amplifier according to the indication from the controller; a transmitter configured to transmit the plurality of signals after adjustment to the source.
 11. The system of claim 10, wherein the controller is also configured to increase gains on signals when a downlink signal power from the destination to the system is smaller or equal to a predetermined threshold.
 12. The system of claim 10, wherein the first device comprises a head end, the second device comprises coverage nodes, and the source comprises a telecommunication tower or access point. 